Effective January 26, 2021, all international arrivals to the U.S., including U.S. citizens, will be required to present a negative COVID-19  (RT-PCR, Rapid & Antigen are acceptable tests, Anti-body not accepted) test taken within 72 hours prior to departure to the U.S.  or documentation that they had the infection in the past and have recovered. (No longer than 90 days or shorter than 10 days )

Additionally, every passenger 2 years of age or older must also submit a passenger disclosure and attestation to the United States of America form duly filled and signed at the time of Check-in. A parent or other authorized individual may attest on behalf of a passenger aged 2 to 17 years.

Appended below is a link to the CDC page which also includes the attestation form.

https://www.cdc.gov/quarantine/fr-proof-negative-test.html#_blank

Furthermore, in accordance to the CDC announcement , face masks are a required to be worn in airports, commercial aircraft and in various modes of surface transportation for all flights to, from or within the United states.

https://www.cdc.gov/coronavirus/2019-ncov/travelers/face-masks-public-transportation.html